An error occurred while fetching the assigned iteration of the selected issue.
Name conflict with DerivingDataTypeable, StandaloneDeriving and qualified imports
The bug is triggered by the following minimal example. Types A.A and B.B share a constructor with the same name. Module B is imported qualified, so that the constructors do not conflict.
A.hs:
module A where
data A = C1 | C2 | CB.hs:
module B where
data B = D1 | D2 | CC.hs:
{-# LANGUAGE DeriveDataTypeable #-}
{-# LANGUAGE StandaloneDeriving #-}
module C where
import Data.Data
import Data.Typeable
import A
import qualified B as B
deriving instance Typeable A
deriving instance Typeable B.B
deriving instance Data A
deriving instance Data B.B
main :: IO ()
main = return ()When deriving a Data instance for the types, I get a name conflict for some generated code:
[au@lift ghc-bug]$ ~/Software/ghc-head/bin/ghc --make C.hs
[1 of 3] Compiling B ( B.hs, B.o )
[2 of 3] Compiling A ( A.hs, A.o )
[3 of 3] Compiling C ( C.hs, C.o )
C.hs:12:1:
Duplicate type signatures for ‛$cC’
at C.hs:11:1-24
C.hs:12:1-26
Note that:
- The problem occurs when deriving Data. Deriving Just the Typeable instance does not produce an error.
- Moving the derivation of Typeable and Data to modules A and B respectively works fine.
The problem occurs both in ghc 7.6.2 as well as in ghc head (rev. cfb9bee7).
Trac metadata
| Trac field | Value |
|---|---|
| Version | 7.7 |
| Type | Bug |
| TypeOfFailure | OtherFailure |
| Priority | normal |
| Resolution | Unresolved |
| Component | Compiler |
| Test case | |
| Differential revisions | |
| BlockedBy | |
| Related | |
| Blocking | |
| CC | |
| Operating system | |
| Architecture |
